Analysis: Tracking the source of AIDS

The work was gross, smelly and messy, but when the scientists were finished their dirty work was rewarded with a gem of research: the origin of the virus that causes AIDS.

A quarter of a century after the syndrome was first recognized, doctors said Tuesday they believe they have pinpointed the roots of the epidemic that has killed millions and now infects 40 million others worldwide.

The virus appears to have originated in a community of chimpanzees that lived in southern Cameroon, near the border of present day Gabon and the Congo Republic, said Paul Sharpe, professor of genetics at the University of Nottingham in the United Kingdom.

Sharpe and his colleagues spent 15 years digging in mounds of old chimpanzee feces and then in laboratories when high technology genetic testing and sequencing tools were used to unravel the clues found in West Central Africa.

It took the researchers 15 years of searching to closely match the genetic structure of an animal virus to that of the earliest known example of human immunodeficiency virus, the pathogen that causes AIDS.

That human sample dates to 1959 and was found in a serum sample in Kinshasa, the capital of the Democratic Republic of the Congo, just down a river from where he believes the virus jumped from chimpanzee to a human being. "That jump most likely occurred in the 1930s, our research and that of others indicates," he told United Press International.

"By the time the man in Kinshasa had HIV infection, there were probably thousands of people in the region with the disease," Sharp said Tuesday in discussing his findings at the 13th Conference on Retroviruses and Opportunistic Infections in Denver.

The closest virus in structure to HIV in the animal kingdom is SIVcpz. SIVcpz is found in a subspecies of chimpanzees, Pan troglodytes troglodytes. Sharp tracked families of these chimpanzees in the isolated area of Cameroon, taking samples from dried mounds of feces and then performing molecular sequencing of the samples.

He said the techniques used were completely non-invasive. None of the chimpanzees had to be captured, shot or injected for scientists to retrieve the biological specimens needed to connect the dots and lead to the location of the chimpanzee troop.

Using sophisticated molecular sequencing techniques, Sharp was able to pinpoint a clustering of these early viruses, determining the area where the epidemic appears to have begun.

He said the sequencing of the virus of the man in Kinshasa, with its resemblance to the SIVcpz strain, "is clear evidence that the virus had been circulating in that area 30 years earlier."

"This study is really a remarkable achievement," said John Coffin, professor of molecular biology at Tufts University in Boston. "They have shown the way to settle one of the many issues in HIV research."